Re: [PATCH v3] mm: bypass swap readahead for zswap

[Nhat Pham]

On Mon, Oct 12, 2026 at 1:01 AM Barry Song <baohua@xxxxxxxxxx> wrote:
>
>
> Thanks! This seems to be a strong indication that setting
> `page-cluster = 0` can also resolve your problem, even without your
> patch. :-)

If every tenants use zswap, yes. But we have tenants with different
kinds of swap backend in the same host (some using compressed
synchronous swap backend, some async IO swap backend).

>
> But I'm still glad to see your auto-tuning patch!

I think we need some smarter readahead work, for sure. I'm just not
quite sure what it'd look like in the end, though.

Doing synchronous readahead work in page fault feels wrong. I chatted
very briefly with Kairui about this. Kairui is trying to come up with
smarter readahead heuristics, but I don't know - even if it's 100%
hitrate, we're concentrating work of multiple pagefaults into a single
pagefault. That sounds off to me?

Crazy idea time - what if instead of skipping readahead for
zswap/zram, we offload it to asynchronous worker (only synchronously
loading the target page)? That'll cancel out the latency issue at
least...?

>
> Best Regards
> Barry